RAL Space + Brüel & Kjær…James Webb Space Telescope Prefers To Be Shaken…Not Stirred

[SatNews] The famous quote from James Bond about ‘shaken not stirred’ refers to his martinis, however shaken is also the preferred process for this satellite.

RAL Space provides space research and technology development for customers around the world. They offer space test and ground-based facilities where they design and build instruments, analyze and process data. They also operate ground-station facilities, and lead conceptual studies for future missions.

Working with space and ground-based groups around the world, they are now the largest space science department in Europe, and have been involved in over 150 missions in recent years, including the groundbreaking SOHO and STEREO solar missions, the Earth Remote-Sensing missions ERS-1, ERS-2 and ENVISAT, and solar system missions such as the Rosetta cometary lander, the Cassini/Huygens mission to Saturn and its moon Titan, and continuing work on MIRI (Mid-Infrared Instrument) for the James Webb Space Telescope (JWST).

The James Webb Space Telescope (JWST) is due to be launched in 2018 as the scientific successor to the venerable Hubble Space Telescope. The JWST’s 10-year mission is to find and study the first luminous objects, the assembly of galaxies, the birth of stars, the birth of planetary systems, and the origins of life.

JWST might appear serene, but that fragile mass of technology must endure being stowed as the 6-ton payload of a launch vehicle. The satellite and its components (such as MIRI) must endure the noise and subsequent vibration of the ~145 dB interaction between the rocket engines and launch-pad environment, the jarring transonic climb phase, pyroshock as stages separate, turbulent boundary layer excitation and more.

In 2010, RAL Space decided to replace their existing LDS V954 Vibration System with a more powerful and flexible one to meet its increased testing needs. Their older V954 had served them well, but with increasing payload masses and more severe tests required, RAL Space needed to improve their capabilities.

The new solution provides the increased capacity necessary for test programs going forward, and is based on the Brüel & Kjær’s LDS V8 electro-dynamic shaker, with the ability to operate in horizontal or vertical orientation. An integral slip table measuring 1200 mm x 1200 mm is coupled to the shaker as necessary, allowing large objects to be mounted securely. The slip table has nine high-pressure hydrostatic bearings arranged on a 3 x 3 matrix. This configuration provides for maximum overturning restraint for devices under test with a high centre of gravity. They also have an additional, interchangeable 750 mm x 750 mm slip plate for high acceleration testing.

The amplifier—a 56 kVA class ‘D’ switching amplifier—is forced-air cooled and incorporates an integral DC field power supply which is required for the shaker field coils. The shaker is also forced-air cooled and relies on a fixed blower device to pass air through the shaker for efficient cooling during operation.